check_snprintf.c

   1 /*
   2  * sparse/check_snprintf.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "smatch.h"
  11 #include "smatch_slist.h"
  12 #include "smatch_extra.h"
  13
  14 static int my_id;
  15
  16 static void ok_to_use(const char *name, struct symbol *sym, struct expression *expr, void *unused)
  17 {
  18         delete_state(my_id, name, sym);
  19 }
  20
  21 static void match_snprintf(const char *fn, struct expression *expr, void *info)
  22 {
  23         struct expression *call;
  24         struct expression *arg;
  25         long long buflen;
  26
  27         call = strip_expr(expr->right);
  28         arg = get_argument_from_call_expr(call->args, 1);
  29         if (!get_fuzzy_max(arg, &buflen))
  30                 return;
  31         set_state_expr(my_id, expr->left, alloc_state_num(buflen));
  32 }
  33
  34 static int get_old_buflen(struct sm_state *sm)
  35 {
  36         struct sm_state *tmp;
  37         int ret = 0;
  38
  39         FOR_EACH_PTR(sm->possible, tmp) {
  40                 if ((int)tmp->state->data > ret)
  41                         ret = (int)tmp->state->data;
  42         } END_FOR_EACH_PTR(tmp);
  43         return ret;
  44 }
  45
  46 static void match_call(struct expression *expr)
  47 {
  48         struct expression *arg;
  49         struct sm_state *sm;
  50         int old_buflen;
  51         long long max;
  52
  53         FOR_EACH_PTR(expr->args, arg) {
  54                 sm = get_sm_state_expr(my_id, arg);
  55                 if (!sm)
  56                         continue;
  57                 old_buflen = get_old_buflen(sm);
  58                 if (!old_buflen)
  59                         return;
  60                 if (get_absolute_max(arg, &max) && max > old_buflen)
  61                         sm_msg("warn: '%s' returned from snprintf() might be larger than %d",
  62                                 sm->name, old_buflen);
  63         } END_FOR_EACH_PTR(arg);
  64 }
  65
  66 void check_snprintf(int id)
  67 {
  68         if (option_project != PROJ_KERNEL)
  69                 return;
  70
  71         my_id = id;
  72         add_hook(&match_call, FUNCTION_CALL_HOOK);
  73         add_function_assign_hook("snprintf", &match_snprintf, NULL);
  74         set_default_modification_hook(my_id, ok_to_use);
  75 }
  76